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MODULE ABO Blood Grouping
Hematology and Blood
Bank Technique
7
Notes ABO BLOOD GROUPING
7.1 INTRODUCTION
Several blood group systems have been described in humans. Of these, the ABO
blood group system is most significant.
OBJECTIVE
After reading this lesson, you will be able to:
z explain commonly used terms in ABO grouping
z describe antigen antibody reactions
z describe the basis of ABO grouping.
z explain the techniques of ABO grouping.
7.2 SOME COMMON ASPECTS OF IMMUNO-
HEMATOLOGY
We will learn about some commonly used terms before beginning ABO
grouping. This will help in better understanding of the subject.
Antigen: An antigen is a substance usually a protein which when introduced into
an individual who recognizes it as foreign, leads to the production of antibody.
This antibody specifically reacts with the antigen.
On the red cell surface there is presence of glycoproteins and glycolipids which
act as antigens. They are called blood group antigens. These antigens can be
on the surface, below or protrude from the red cell membrane. If introduced into
the body of an individual who lacks the antigen, an immune reaction can occur.
Antibodies: These are immunoglobulins present in the serum and can be of 5
types: IgG, IgM, IgD, IgA and IgE.
48 HEMATOLOGY AND BLOOD BANK TECHNIQUE
ABO Blood Grouping MODULE
If red cells carrying an antigen are introduced into the circulation of an individual Hematology and Blood
who lacks that antigen, antibodies will form and cause destruction of the Bank Technique
introduced red cells. These are immune or acquired antibodies and are IgG in
nature. They react best at 37°C.
Certain antibodies occur without antigenic stimulus and are called naturally
occurring antibodies e.g. ABO antibodies. They are IgM in nature and react
at room temperature. Notes
INTEXT QUESTIONS 7.1
1. Substance leading to production of antibody is .....................
2. ..................... & ..................... acts as antigens.
3. Immunoglobulin of sera are .....................
4. Antibodies are ..................... present in sera.
5. Antibodies without antigenic stimulus is called as .....................
7.3 ANTIGEN ANTIBODY REACTIONS
The antigen antibody reactions relevant to blood banking are:
z sensitization
z agglutination
z hemolysis
z neutralization
Sensitization is the combination of antigen and antibody. This is a reversible
reaction.
Agglutination is the clumping of red cells. It occurs when sensitized cells come
into contact with each other resulting in formation of bridges between them and
formation of aggregates. It is the most common procedure in blood banking.
Hemolysis as the name suggests is destruction of red cells resulting in the release
of hemoglobin from the cells due to the action of complement. This is used in
antibody screening tests.
Neutralization: Blood group antigens when added to serum containing antibody
can neutralize it. This is used in determining secretor status. If the strength of
the antibody reduces, the antigen antibody reaction is assumed to have occurred.
Genotype: This refers to the genes present on the chromosome inherited from
each parent irrespective of whether they produce any product which is
detectable.
HEMATOLOGY AND BLOOD BANK TECHNIQUE 49
MODULE ABO Blood Grouping
Hematology and Blood Phenotype: This is used to describe the observable effect of the inherited genes
Bank Technique or expression of the genes i.e. the blood group.
INTEXT QUESTIONS 7.2
Notes Match the following
1. Sensitization (a) Observable effect of the inherited genes
2. Agglutination (b) Destruction of red cells
3. Hemolysis (c) Genes on chromosome
4. Genotype (d) Combination of antigen & antibody
5. Phenotype (e) Clumping of red cells
7.4 ABO BLOOD GROUP SYSTEM
The ABO grouping system is subdivided into 4 types based on the presence or
absence of antigens A and B on the red cell surface as shown below. Red cells
that only have antigen A are called group A. Those that only have B antigen are
called group B. Cells that have both A and B antigens are group AB. Cells that
lack both antigens are O.
7.5 ANTIBODIES
The ABO antibodies ; anti-A and anti-B are naturally occurring antibodies and
are present in the sera of individuals who lack the corresponding antigen. Cells
with A antigen will have anti-B in the serum. Cells with B antigen will have
anti-A in the serum and cells with AB antigens will not have any antibody.
Group O individuals will have both anti-A and anti-B antibodies. These
antibodies are IgM in nature.
The antigens and the corresponding antibodies in each blood group are shown
below.
Table 7.1
Group Antigen Antibody
A A Anti-B
B B Anti-A
AB A and B None
O None Anti-A, Anti-B
50 HEMATOLOGY AND BLOOD BANK TECHNIQUE
ABO Blood Grouping MODULE
Genetics: All features in humans are controlled by genes present on Hematology and Blood
chromosomes. Each cell has 23 pairs of chromosomes. There is one locus on Bank Technique
chromosome 9 occupied by one of the three alleles A, B, O. The genes of the
ABO system are inherited as mendelian codominant. Each individual inherits
one gene from each parent. The chromosome from the mother carries one of A,B
or O gene. Similarly the chromosome from the father also has one of A, B or
O gene. The gene on each chromosome determines the blood group as shown
below. The A and B genes are dominant over the O gene. Notes
Table 7.2
Father Mother
OO AA Genotype
Children AO AO AO AO Genotype
Blood group of children A A A A Phenotype
Mother group A, father group O and all children are group A.
INTEXT QUESTIONS 7.3
Match the following
Blood Group Antigen
1. Group A (a) Has both A & B antigen
2. Group B (b) Antigen A
3. Group C (c) Lack of A & B antigen
4. Group D (d) Antigen B
Technique of ABO grouping: Various techniques are available for ABO
grouping in the laboratory. These are
1. Slide technique
2. Tube technique
3. Microplate technique
4. Gel card technique
Slide technique
This can be performed in emergency or outdoor camps but must not be
performed as a routine test.
HEMATOLOGY AND BLOOD BANK TECHNIQUE 51
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